Filter apparatus



2 Sheets-Sheet 1 Filed Jan. 5, 1967 INVENTOR. HANS H. BALBIERER A3 TTOIQNEVS Dec. 16, 1969 H, H. BALBIERER 3,483,679

FILTER APPARATUS Filed Jan. 5, 1967 2 Sheets-Sheet 2 INVENTOR. HANS H. BALBIERER United States Patent 3,483,679 FILTER APPARATUS Hans H. Balbierer, Fairport, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Jan. 3, 1967, Ser. No. 606,889 Int. Cl. B01d 46/ 04 US. Cl. 55-367 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to filter bags and, in particular, to an improved filter bag assembly for removing xerographic toner particles from air in the exhaust system of the plate cleaning station of a xerographic reproducing machine.

More specifically, this invention relates to a throwaway filter bag, having a combined closure valve and a mounting flange forming a handle portion to facilitate the insertion and removal of the filter bag from the suction cleaner.

In the xerographic process, a xerographic plate comprising a photoconductive insulating material on a conductive backing, is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate in accordance with the light intensity which reaches a plate thereby creating an electrostatic latent image on or in the plate surface.

Development of the electrostatic latent image is usually effected by electrostatically attractable material which is generally a thermoplastic resin in the form of finely divided particles usually in the size range from 3 to microns, commonly referred to as toner or toner powder. In the development of the electrostatic latent image, the toner powder is brought into surface contact with the photoconductive surface and it is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. The developed image is then transferred to a suitable support material, such as paper, and fused thereon to make a permanent image. In the xerographic transfer step substantially all of the resin material or toner powder is caused to adhere to the support material to form the images thereon, but usually a very small percentage of the resin material or toner remains on the xerographic plate.

The small quantity of resin material or toner powder remaining on the xerographic plate will affect future operating steps of the xerographic process and if left remaining thereon has an accumulative effect in that additional residual toner powder particles would adhere more readily to the xerographic plate in both image and non-image areas.

To clean the xerographic plate of the residual toner powder adhering thereto, there is disclosed in Turner et a1. Patent No. 2,751,616, a rotating brush in peripheral contact with the surface of the xerographic plate to clean the photo-conductive surface of any residual resin material or toner powder adhering thereto. The brush is positioned adjacent to a vacuum system, similar in structure to that of the common household vacuum cleaner, whereby the residual resin material or toner powder is entrained in air and then filtered from the air by a suitable filter device.

3,483,679 Patented Dec. 16, 1969 It is an object of this invention to improve xerographic filtering apparatus utilizing a filter bag having a closure valve for retaining the contents within the filter bag upon the removal of the filter bag from the filter apparatus.

Another object of this invention is to improve xero graphic filtering apparatus by adapting the filter bag mounting apparatus to facilitate the insertion and re moval of the filter bag from the filtering apparatus.

It is a further object of this invention to improve xerographic filtering apparatus utilizing a filter bag having a closure portion adapted to contain the contents within the filter bag and having a mounting flange including a handle portion to provide a convenient means for inserting and removing the filter bag from the filter housing.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a xerographic reproducing machine having a filter box and filter bag, constructed in accordance with one of the embodiments of the invention;

FIG. 2 is a perspective view of the filter bag of FIG. 1 showing the mounting flange and closure valve;

FIG. 3 is a perspective view of the filter bag of FIG. 2 with the mounting flange removed to better illustrate the internal closure valve.

Referring now to the drawings, there is shown in FIG. 1 an automatic xerographic reproducing machine including a xerographic plate 1 having a photoconductive layer or light receiving surface on a conductive backing, journaled in a frame to rotate in the direction indicated by the arrow to cause the plate surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in a path of movement of the plate surface may be described functionally, as follows:

A charging station 2 at which a uniform electrostatic charge is deposited on or in the photoconductive plate surface;

An exposure station 3 at which a light or radiation pattern of copy to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copy to be reproduced;

A developing station 4 at which xerographic developing material including toner powder particles having an elecrostatic charge opposite to that of the electrostatic latent image are cascaded over the plate surface, whereby the toner powder adheres to the electrostatic latent image to form a toner-powder image in the configuration of the copy being reproduced;

A transfer station 5 at which the toner-powder image is electrostatically transferred from the plate surface to a transfer material or a support surface; and

A drum cleaning and discharge station 6 at which the plate surface is brushed to remove residual toner particles remaining thereon after image transfer, and at which the plate surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

It is felt that the preceding description of the xerographic process is sufficient for a better understanding of this invention. Referring now to the subject matter of the invention, as shown in FIGS. 1-3, the plate cleaning assembly, generally designated 20, comprises a rotatable brush 21 of such construction as to apply extremely light pressure to the photoconductive surface of the xerographic drum to dislodge any particles of re- J sidual resin or toner powder that may adhere thereto. The brush 21, is mounted within a hood 22 encompassing approximately /4 of the brush area and is used for containing the particles of residual resin or toner powder removed from the drum by the brush.

A motor-driven centrifugal blower, not shown, is connected by a suitable duct system to the hood 22 to draw air through the area surrounding the xerographic drum and the hood. This air will entrain particles of residual resin or toner powder removed from the xerographic drum by the brush. Residual resin or toner powder particles are separated from the air by a filter bag 30, to be described in detail hereinafter, so that toner free air reaches the motor-driven centrifugal blowers.

To prevent a high pressure drop through the filter 30, the filter is formed in the shape of a bag and it is positioned in an enlarged portion of the discharge duct, this enlarged portion being in the form of a filter box 29 having a removable panel or front cover for access into the interior of the filter box.

In the arrangement of the plate cleaning apparatus Shown, a duct is connected at one end to the discharge conduit in th back of hood 22, and at its other end the duct is connected by an appropriate adapter with an aperture in the filter box. Manifold outlet conduits of the filter box 29 are connected to the inlets of the motordriven centrifugal blower.

The filter bag 30 is formed with an inner wall of glass wool fibers (fiber glass) loosely assembled into a web or mat of progressive density and an outer wall of loosely assembled glass wool fibers into a web or mat of substantially uniform density to form a self sustaining structure.

The filter bag 30 is constructed whereby the flow of air, contain the particles of residual resin or toner powder, travels through the filtering medium of progressively increasing density and then through a filtering medium of substantially uniform density, the filtering media being a loosely assembed web or mat of fiber glass.

In the embodiment of the filter bag arrangement shown in the figures, a single mat of fiber glass having, in cross section, an area of progressive density and then an area of uniform density may be used in fabricating the filter bag or, as shown, the filter bag may be formed from two mats of fiber glass, a flat blank fiber glass mat material of progressive density to form the inner walls of the filter bag and a flat blank of fiber glass mat material of substantially uniform density to form the outer wall of the filter bag, the denser side of the blank being positioned adjacent the surface of the uniform density blank.

Both of the blanks are cut to form an inlet aperture and have an apertured inner flange 42 secured to the inner surface of the inner blank, for example, by a staple in each corner, the stapling being done from the inner side of the blank. An outer apertured bearing flange 43 is secured to the outer surface of the outer blank. Both flanges 42 and 43, made for example, of cardboard or other stiff material, are positioned with the openings in the gasket in alignment with the inlet passage of the blanks. An apertured compressible gasket 44 is secured as by cement to the top of outer bearing flange 43. The compressible gasket 44 has an opening 45 in one side for a purpose to be hereinafter described in detail. A closure valve 46 is slidably positioned within the aperture of compressible gasket 44 and is adapted to be moved into interference between the apertures of the filter bag and flanges, to form a closure thereof to contain the contents of the filter bag therein when the bag is being removed from the filter box 29. A cord 47 is secured at one end to the closure valve 46 and at the other end to a suitable spool to allow the closure valve to be drawn between the apertures prior to removal of the filter bag from the filter box 22. An apertured mounting flange 48, made for example, of the same material as flange 43, is secured as by cement on top of the compressible gasket 44. The flanges 44 and 48 are substantially rectangular in the form shown in FIGS. 2 and 3, with apertures of a suitable size and shape to correspond to the discharge opening in the top of the filter box. The lower flange 43 extends beyond the mounting flange 48 and is formed with an opening or handle portion 53 to facilitate the insertion and removal of the filter bag 30 from the filter box 29. The assembled filter bag 39 is mounted in the filter box, whereby the filter bag is seated against the upper wall of the filter box with the filter media extending downstream. The top wall of the filter box, which has an opening forming the discharge opening from the hood 22 into the filter box, is formed with an apertured compressible gasket 28 axially aligned with the opening, to

form a dust-proof seal between the gasket 28 and the upper flange 48 of the filter bag when the filter bag is in operative position within the filter box 29.

The filter bag 30 is inserted into operative position within the filter box 29 to form a dust-proof seal by grasping the handle 53 and inserting the upper flange 48 of the filter bag into a pair of slide members 26 and 27 extending parallel to each other at the sides of the opening in the filter box and having turned portions adapted to engage the upper flange 48 to form a dustproof seal by means of the compressible gasket 28 and the flange 43 being pressed together. The filter bag 30 is secured in operative position within the filter box 29 by grasping the handle 53 and inserting the upper flange 48 onto the slides 26 and 27, with the turned portions of the slides being between the flanges 43 and 48, to compress the gasket 28 to form a dust-proof seal. The lower bearing flange 43 which extends beyond the turned portion of the slides protects the fragile filtering material from being torn during the insertion of the bag into the filter box.

After the filter bag has been used for a period of approximately 18 hours of machine operation, the normal maximum useful life, the bag may be replaced by drawing on the cord 47 to slide the closure valve 46 into interference with the normal path of aeriform fluid passing from the duct into the filter bag to thereby contain the contents within the bag, and grasping the handle 53 to pull the bag from the slides 26 and 27.

What is claimed is:

1. A toner tight xerographic filtering apparatus for storing and removing residual toner cleaned from a photoconductive plate surface in a xerographic machine including:

(A) rotary brush means for dislodging the residual toner from the plate surface, said brush means applying an extremely light pressure to said photoconductive plate surface;

(B) housing means for containing said brush means, said housing means encompassing approximately three fourths of the brush surface area;

(C) a filter box having a top wall and an inlet aperture in said top wall;

(D) a toner tight duct operatively connected to said brush housing means for conducting toner out of said brush housing means and having a dependant outlet end;

(E) an appropriate adapter operatively connecting said outlet end of said duct to said inlet aperture of said filter box;

(F) a filter bag of air pervious material having an inner wall of progressively denser glass wool fibers assembled in a web and an outer wall of loosely assembled glass wool fibers made into a web of uni form density to form a self sustaining structure having an inlet opening therein for communicating with said outlet end of said duct;

(G) a pair of slide members each having a horizontally extending inwardly turned support flange and each slide member being attached to the underside of said top wall, said flanges being spaced apart from and parallel to one another, one of said slide members positioned on one side of said inlet opening and the other of said slide members being positioned on the side of said inlet opening opposite to said one side;

(H) a first apertured compressible gasket secured to the underside of said top wall with the aperture in said first gasket being axially aligned with the inlet aperture in said top wall, said first gasket being disposed between said slide members;

(I) an apertured bearing flange operatively coacting with said support flanges;

(I) said bearing flange being constructed of a relatively stifl material which is secured to said filter bag so the aperture therein is axially aligned with the filter bag inlet opening;

(K) a second apertured compressible gasket secured to said bearing flange such that the aperture therein is axially aligned with said bearing flange aperture and said compressible gasket carrying internally in slidable relation therewith a closure valve;

(L) an apertured mounting flange constructed of a relatively stilt material secured to said compressible gasket so that said mounting flange aperture is axially aligned with said bearing flange aperture;

(M) said second gasket being sandwiched between said mounting flange and said bearing flange;

(N) said mounting flange and said bearing flange being wider than said second compressible gasket and together with said second gasket form a pair of grooves, each of said grooves receiving in tight slidable relation therein a respective one of said inwardly turned support flanges wherein pressure is exerted on said first compressible gasket by said mounting flange and a toner tight seal is formed between said mount- 3 ing flange and said top wall;

(0) said closure valve which is slidably carried within said second compressible gasket being supported upon said apertured bearing flange such that said closure valve is movable in the second compressible gasket aperture from a position not between the bearing flange aperture and the mounting flange aperture to a position between the bearing flange aperture and the mounting flange aperture to close the filter bag inlet opening toner tight to prevent leakage of toner from said filter bag through said filter bag inlet opening;

(P) means operable to actuate the closure valve, said means comprising a spool attached to said bearing flange, a small passageway through said second gasket, a cord attached at a first end thereof to said closure valve, said cord extending from said closure valve through said passageway and having its second end opposite said first end removably wound around said spool whereby said cord may be unwound from said spool and pulled to move said closure valve into closed position to close said filter bag inlet and rewound on said spool to maintain said valve in closed position;

(Q) means formed by said bearing flange to facilitate insertion and removal of said receptacle in and out of engagement with said support flanges, said means comprising an aperture formed in a portion of said bearing flange extending beyond the filter bag; and

(R) means for exhausting air entrained powder material from said housing means through said duct to said filter bag.

References Cited UNITED STATES PATENTS 2,079,896 5/1937 Brosius 251-150 2,218,169 10/1940 Hudson 251144,9 2,590,235 3/1952 Cranmer 367 2,721,625 10/ 1955 Lagerstrom 55372 2,752,002 6/1956 Wied 55376 2,804,167 8/1957 Seck 55367 2,805,836 9/1957 Taylor 251177 2,864,462 12/1958 Brace 55373 X 3,047,006 7/1962 Transedu 251177 X 3,197,118 7/1965 Meyerhoefer 55361 X 3,238,706 3/ 1966 Kurlinski 15327 X 3,252,274 5/1966 Benson et a1 55--377 3,260,038 7/1966 Casady 55367 X 3,410,060 11/1968 Reilly et al. 55481 X FOREIGN PATENTS 2/1966 Great Britain.

OTHER REFERENCES HARRY B. THORNTON, Primary Examiner DENNIS E. TALBERT, Assistant Examiner US. Cl. X.R. 

